I have a 2017 A8L with the 380mm front discs. I replaced my front discs and pad just over 2 weeks ago. Did everything correctly as far as I can tell. The only thing that I did that others have suggested not to do is that I did not bleed the piston when I pushed it back in to replace the pads. Instead I let it flow back into the reservoir. After finishing the pedal would get firm but not stay firm. With the car turned off the pedal would get firm but then soft after about a min or so. With the car running I had to pump the brakes to get them firm and stop. They would soon get soft and the pedal would go almost to the floor. I was told by a former audi tech that I likely broke a seal in the master cylinder. I bought a new one and was going to test the old one, BUT I got wrong plugs and to save time I went ahead and replaced. . . . . Forgot to bench bleed but bled with it on the car after installing. Then thoroughly, and I do mean thoroughly, bled per repair manual sequence. But alas the problem remains. Almost exactly how it was before replacing master cylinder. I cant find any leaks anywhere. However, one of the front right caliper pistons has some seepage possibly. I can attach photo if anyone would like.
Any troubleshooting suggest would be appreciated.
Calling today to get it into the shop, but if theres anything to try before then i'm willing to try.
I've read maybe bleed ABS?
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